Your body is made up of trillions of cells. Each cell has a core structure (nucleus) that contains your chromosomes.

Each chromosome is made up of tightly coiled strands of deoxyribonucleic acid (DNA). Genes are segments of DNA that determine specific traits, such as eye or hair color. You have more than 20,000 genes. You have two copies of each gene — one inherited from each of your parents.

A mutation is a change in your DNA. A gene mutation is a change in or damage to a gene. A mutation can be inherited or acquired during your lifetime as cells age or are exposed to certain chemicals. These changes in your DNA can result in genetic disorders.

Legal Conditions and Terms

Reprint Permissions

A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.org," "Mayo Clinic Healthy Living," and the triple-shield Mayo Clinic logo are trademarks of Mayo Foundation for Medical Education and Research.